1. Field of the Invention
This invention generally relates to the field of non-contact bearings, and more particularly, to an axial hybrid magnetic bearing, method for operation thereof, and structure for rotor thereof.
2. Description of the Prior Art
The active magnetic bearings (AMB) are non-contact bearings and they are increasingly being used in industrial applications, for example, the spindle of machine tool, energy storage flywheels and turbo-molecular pumps, etc. In the vertical rotary mechanism, the axial bearing suffered the most loading to suspend the rotor. In these applications, the electric-magnet-biased axial magnetic bearings will consume a lot of electric power.
In order to reduce the electric power, there are many researches about the hybrid magnetic bearings (HMB) to lower the power consumption, such as Sortore C. K., Allaire P. E., Maslen E. H., Humphris R. R. and Studer P. A., “Permanent magnet biased magnetic bearings-design, construction and testing,” Proceedings of 2nd international symposium on magnetic bearings Tokyo Japan, pp. 12-4, 1990, Satoru FUKATA, Kazuyuki YUTANI and Yoshinori KOUYA, “Characteristics of Magnetic Bearing Biased with Permanent Magnets in the Stator,” JSME Int. J., Ser. C, Vol. 41, No. 2, pp. 2006, 1998, and Xu Yanliang, Dun Yueqin, Wan Xiuhe and Kong Yu, “Analysis of Hybrid Magnetic Bearing With a Permanent Magnet in the Rotor by FEM,” IEEE Transaction on Magnetics, Vol. 42, No. 4, pp. 1363, 2006. From the data in these researches, we know that the hybrid magnetic bearings are useful than traditional active magnetic bearings.
And there are many researches which concerning the permanent magnet to be a novel design, for example, Han W. S., Lee C. W. and Okada Y., “Design and control of a disk-type integrated motor-bearing system,” IEEE/ASME Tran. Mechatron., Vol. 7(1), pp. 15-22, 2002, Okada Y., Konish H., Kanebako H. and Lee C. W., “Lorentz force type self-bearing motor,” Proceedings of 7th international symposium on magnetic bearings, pp. 353-358, 2000, and Maslen E. H., Allaire P. E., Noh M. D. and Sortore C. K., “Magnetic bearing design for reduced power consumption,” ASME J. Trib., Vol. 118, pp. 839-846, 1996. But the designs of these HMB are not consider of the magnetic flux coupling, so the electric magnetic flux will pass through the permanent magnets. That is, the permanent magnets are magnetizing and de-magnetizing as the electric magnets work. The operation situation will demand the performance of the permanent magnets.
In view of the drawbacks mentioned with the prior art of HMB, there is a continuous need to develop a new and improved HMB that overcomes the shortages associated with the prior art of HMB. The advantages of the present invention are that it solves the problems mentioned above.